Defense Date

2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Psychology

First Advisor

Kenneth Kendler

Abstract

Eating disorders and substance use disorders both exhibit a clear sex-difference in prevalence. Eating disorders are more common in females while substance use disorders are more common in males. Previous research has also established a strong association between these two disorders, especially within females. Much less research has examined comorbity in males. The etiology and reasons for these sex-differences and for the comorbidity of eating and substance use disorders remain unclear. The present report aimed to examine disordered eating (DE), substance use (SU), and their comorbidity further, in both sexes, using disorder eating attitudes and behaviors and substance use rather than diagnoses. DE was examined with the Drive for Thinness, Bulimia, and Body Dissatisfaction subscales of the Eating Disorder Inventory-II. Nicotine, alcohol, and illicit drug use was also assessed. Male and female twin pairs from The Swedish Twin study of CHild and Adolescent Development will be used which includes 1,480 twin pairs assessed at three age points; 13-14, 16-17, and 19-20. A twin design was utilized to examine important aspects of the genetic and environmental risk factors for DE, SU, and their comorbidity within three distinct studies. In Study I multivariate twin designs were used and revealed that an underlying common factor was responsible for the three facets of DE in both sexes at age 16-17. Sex-differences were exhibited within these genetic influences such that only 50% of the genetic risk for the DE factor is shared between the sexes. Total heritabilities for the three subscales were higher for females. In Study II a longitudinal, multivariate twin design was used and revealed that an underlying common factor was responsible for SU at all three assessment ages. In general, genetic effects became more substance specific, and common shared environmental effects decreased across the age groups. In Study III, the genetic and environmental covariance between the DE and SU common factors at age 16-17 was examined. The covariance between DE and SU was partly mediated through familial factors, and these factors impacted covariance similarly in the sexes. Genetic and shared environmental factors each accounted for approximately 50% of covariance.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

July 2009

Included in

Psychology Commons

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